Biomedical devices having improved surface characteristics

ABSTRACT

Biomedical devices, such as ophthalmic lenses, and methods of making such devices having a surface coating including at least one polyionic layer. A preferred method involves spray coating a polycationic material onto a core lens, rinsing and drying the lens, followed by spray coating a polyanionic material, rinsing and drying. The coating process may be applied a plurality of times to achieve a multi-layer coating on the lens surface. A particularly preferred embodiment is a contact lens comprising a highly oxygen permeable hydrophobic core coated with a 5 to 20 bilayers of hydrophilic polyionic materials.

This application is a continuation of U.S. patent application Ser. No.12/454,122 filed May 13, 2009, now U.S. Pat. No. 7,705,067 which is acontinuation of U.S. patent application Ser. No. 11/981,206 filed Oct.31, 2007, now U.S. Pat. No. 7,566,746 which is continuation of U.S.patent application Ser. No. 10/202,758, filed Jul. 24, 2002, now U.S.Pat. No. 7,297,725 which is a divisional application of application Ser.No. 09/559,945, filed Apr. 27, 2000; now U.S. Pat. No. 6,451,871 whichis a divisional application of application Ser. No. 09/199,609, filedNov. 25, 1998, now abandoned; which application claimed priority toprovisional application Ser. No. 60/135,513, which was converted to aprovisional application by petition from non-provisional applicationSer. No. 09/005,317, filed Jan. 9, 1998.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to surface treatment technology for biomedicaldevices, and in particular, methods of altering the hydrophobic orhydrophilic nature of the polymeric surface of an ophthalmic lens suchas a contact lens. In one preferred embodiment, this invention relatesto methods of treating biomedical devices, such as contact lenses, toincrease the hydrophilicity of the surface.

2. Description of the Related Art

Many devices and materials used in various biomedical applicationsrequire certain properties in the bulk of the device or material withdistinct and separate properties required for the surface. For example,contact lenses preferably have high oxygen permeability through the lensto maintain good corneal health, but the materials which typicallyexhibit exceptionally high oxygen permeability (e.g. polysiloxanes) arehydrophobic and will adhere to the eye. Thus, a contact lens may have acore or bulk material which is highly oxygen permeable and hydrophobic,and a surface which has been treated or coated to increase thehydrophilicity, thereby allowing the lens to freely move on the eye.

In order to modify the hydrophilicity of the a relatively hydrophobiccontact lens material, a contact lens may be treated with a plasmatreatment. A high quality plasma treatment technique is disclosed in PCTPublication No. WO 96/31792 by inventors Nicolson, et al. However, someplasma treatment processes require significant investment in equipment.Moreover, plasma treatment requires that the lens be dry before exposureto the plasma. Thus, lenses which are wet from prior hydration orextraction processes must be dried, imposing costs of drying equipmentand adding time to the overall lens production process. Accordingly,there remains a need for an inexpensive method of consistently andpermanently altering the surface properties of polymeric biomaterials,especially ophthalmic lenses such as contact lenses. A particularlypreferred method would be one which could be used directly on wetlenses, i.e., without requiring a preliminary drying step.

In contrast to the plasma surface treatment methods used in theophthalmic lens art, a number of techniques have been used to treat thesurface of electronic devices, thin film sensors and the like. Thesetechniques include Langmuir-Blodgett deposition, controlled spincasting, chemisorptions and vapor deposition. Useful examples ofLangmuir-Blodgett layer systems are disclosed in U.S. Pat. Nos.4,941,997; 4,973,429 and 5,068,318 issued to Decher, et al., andassigned to Ciba-Geigy Corporation. A more recent technique used onelectronic devices is a layer-by-layer polymer adsorption process whichis described in “Investigations of New Self-Assembled Multilayer ThinFilms Based on Alternately Adsorbed Layers of Polyelectrolytes andFunctional Dye Molecules” by Dongsik Yoo, et al. (1996).

The Yoo, et al. process involved alternatively dipping hydrophilic glasssubstrates in a polyelectrolyte solution (e.g., polycations such aspolyallylamine or polyethyleneimine) and an oppositely charged dyesolution to form electrically conducting thin films and light-emittingdiodes (LEDs). After each dipping, the substrates were rinsed withacidic aqueous solutions. Both the dipping and rinsing solutions had apH of 2.5 to 7. Prior to dipping, the surfaces of the glass substrateswere treated in order to create a surface having an affinity for thepolyelectrolyte.

Similarly, two 1995 publications entitled “Molecular-Level Processing ofConjugated Polymers” by Fou and Rubner and by Ferreira and Rubner,describe similar methods of treating glass substrates which havehydrophilic, hydrophobic, negatively or positively charged surfaces. Theglass surfaces are treated in hot acid baths followed by hotperoxide/ammonia baths for extended periods to produce a hydrophilicsurface. Hydrophobic surfaces are produced by gas-phase treatment in1,1,1,3,3,3-hexamethyldisilazane for 36 hours. Charged surfaces wereprepared by covalently anchoring charges onto the surface of thehydrophilic slides. For example, positively charged surfaces were madeby further treating the hydrophilic surfaces in methanol,methanol/toluene and pure toluene rinses followed by immersion in(N-2-aminoethyl-3-aminopropyl) trimethyloxysilane solution for 12-15hours. This procedure produced glass slides with amine functionalities,which are positively charged at low pH. All of the substrate surfacepreparations require chemical processing and are time consuming.

U.S. Pat. Nos. 5,518,767 and 5,536,573 issued to Rubner, et al. andassigned to Massachusetts Institute of Technology, describe methods ofproducing bilayers of p-type doped electrically conductive polycationicpolymers and polyanions or water-soluble, non-ionic polymers on glasssubstrates. Extensive chemical pretreatments of the glass substrates,which are the same or similar to those taught in the aforementionedarticles, are described in the '767 and '573 patents.

The layer-by-layer polyelectrolyte deposition methods described inpatent and literature references relate generally to production ofelectronic devices and treatment of rigid glass substrates. Notably, theteachings indicate that complex and time-consuming pretreatment of thesubstrate is required to produce a surface having a highly charged,hydrophilic or hydrophobic nature in order to bind the polycationic orpolyanionic material to the glass substrate.

SUMMARY OF THE INVENTION

An object of the invention is to provide a method of treating polymers,in particular ophthalmic lenses, to alter surface properties.

Another object of the invention is to reduce the complexity ofophthalmic lens production processes.

A further object of the invention is to provide contact lenses having abalance of excellent oxygen permeability though the lens and sufficienthydrophilicity on the surface to permit free movement of the lens whenpositioned on the eye of a wearer.

Yet another object of the invention is to reduce to the material andmanpower costs of producing high quality contact lenses.

Still a further object of the invention is to provide a method ofaltering the surface properties of a wet ophthalmic lens withoutrequiring a prior drying step.

The aforementioned objects and other advantages of the invention areapparent from the following summary and detailed description of theinvention.

One embodiment of the invention is a polymeric device, preferably abiomedical device, comprising a core material and a surface coating. Thesurface coating includes at least one bilayer of polyelectrolytes. Thebilayer includes a first polyionic material which is bonded to the corematerial and a second polyionic material, having charges opposite of thecharges of the first polyionic material, which is bonded to the firstpolyionic material.

Another embodiment of the invention is a method producing a biomedicaldevice having a core material and a surface coating including at leastone bilayer of polyionic materials, including the steps of contacting acore material with a first polyionic material, thereby bonding saidpolyionic material to said core material to form a coated biomedicaldevice; and contacting said coated device with a second polyionicmaterial having charges opposite of the charges of said first polyionicmaterial, thereby forming a biomedical device having a polyionicbilayer.

A group of preferred core materials are those having no substantialsurface charge density. A preferred biomedical device is an ophthalmiclens, especially a contact lens.

Still Another embodiment of the invention is a fixture for supporting anarticle, including a core material having a disperse plurality oftransitory or permanent charges on or near the surface of the materialand a surface coating, including a polyionic material which is bonded tothe core material.

A further embodiment of the invention is a mold for manufacturing anarticle, which includes a core material having a disperse plurality oftransitory or permanent charges on or near the surface of the materialand a surface coating, including a polyionic material which is bonded tothe core material.

Yet a further embodiment of the invention is a method of forming anarticle and coating the article by transfer grafting a coating materialfrom the mold in which the article was produced, comprising the steps of(a) applying a coating of a polyionic material to a mold, (b) dispensinga liquid molding material into the mold, (c) allowing the mold coatingto transfer from the mold to the molding material, and (d) causing theliquid mold material to harden (e.g., by polymerization) to form a solidmolded article having a polyionic coating.

Still another embodiment of the invention is a method of altering thesurface of an article, including the steps of (a) applying to an articlea coating of a polyionic material including functional groups and (b)contacting the coated article with a material reactive to the functionalgroups to graft the material onto the polyionic coating.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention include a biomedical device, suchas an ophthalmic lens, having a polyelectrolyte surface treatment and amethod of applying the surface treatment to a biomedical device. Aparticularly preferred embodiment is an contact lens having a highlyoxygen permeable hydrophobic core and a hydrophilic surface or surfaces.In order to better clarify the technology, certain terms will be definedbefore describing the details of the invention.

The term “biomedical device”, as used herein, includes a wide variety ofdevices used in the biological, medical or personal care industries.Biomedical devices include, without limitation thereto, ophthalmiclenses, drug delivery devices such as oral osmotic devices andtransdermal devices, catheters, contact lens disinfection and cleaningcontainers, breast implants, stents, artificial organs and tissue andthe like.

“Ophthalmic lenses”, as used herein, refers to contact lenses (hard orsoft), intraocular lenses, eye bandages and artificial corneas. In apreferred embodiment, an “ophthalmic lens” refers to lenses which areplaced in intimate contact with the eye or tear fluid, such as contactlenses for vision correction (e.g., spherical, toric, bifocal), contactlenses for modification of eye color, ophthalmic drug delivery devices,ocular tissue protective devices (e.g., ophthalmic healing promotinglenses), and the like. A particularly preferred ophthalmic lens is anextended-wear contact lens, especially extended-wear contact lenses forvision correction.

“Hydrophilic”, as used herein, describes a material or portion thereofwhich will more readily associate with water than with lipids. A“hydrophilic surface”, as used herein, refers to a surface which is morehydrophilic (i.e., more lipophobic) than the bulk or core material of anarticle. Thus, an ophthalmic lens having a hydrophilic surface describesa lens having a core material having a certain hydrophilicitysurrounded, at least in part, by a surface which is more hydrophilicthan the core.

“Polyion” or “polyionic material”, as used herein, refers to a polymericmaterial including a plurality of charged groups, which includespolyelectrolytes, p- and n-type doped conducting polymers. Polyionicmaterials include both polycations (having positive charges) andpolyanions (having negative charges).

I. Coating Processes and Materials

A. Coating Processes

One embodiment of the invention is a method producing an ophthalmic lenshaving a core material and a surface coating including at least onebilayer of polyionic materials, including the steps of contacting a corelens with a first polyionic material, thereby bonding the polyionicmaterial to the core lens to form a coated lens; and contacting thecoated lens with a second polyionic material having charges opposite ofthe charges of the first polyionic material, thereby forming a contactlens having a polyelectrolyte bilayer.

Application of the coating may be accomplished in a number of ways. Onecoating process embodiment involves solely dip-coating and dip-rinsingsteps. Another coating process embodiment involves solely spray-coatingand spray-rinsing steps. However, a number of alternatives involvesvarious combinations of spray- and dip-coating and rinsing steps may bedesigned by a person having ordinary skill in the art.

One dip-coating alternative involves the steps of applying a coating ofa first polyionic material to a core lens by immersing said lens in afirst solution of a first polyionic material; rinsing the lens byimmersing the lens in a rinsing solution; and, optionally, drying saidlens. This procedure is then repeated using a second polyionic material,with the second polyionic material having charges opposite of thecharges of the first polyionic material, in order to form a polyionicbilayer.

This bilayer formation process may be repeated a plurality of times inorder to produce a thicker lens coating. A preferred number of bilayersis about 5 to about 20 bilayers. A more preferred number of bilayers isabout 10 to about 15 bilayers. While more than 20 bilayers are possible,it has been found that delamination may occur in coatings having anexcessive number of bilayers.

The immersion time for each of the coating and rinsing steps may varydepending on a number of factors. Preferably, immersion of the corematerial into the polyionic solution occurs over a period of about 1 to30 minutes, more preferably about 2 to 20 minutes, and most preferablyabout 1 to 5 minutes. Rinsing may be accomplished in one step, but aplurality of rinsing steps has been found to be quite efficient. Rinsingin a series of about 2 to 5 steps is preferred, with each immersion intothe rinsing solution preferably consuming about 1 to about 3 minutes.

Another embodiment of the coating process involves a series of spraycoating techniques. The process generally includes the steps of applyinga coating of a first polyionic material to a core lens by contacting thelens with a first solution of a first polyionic material; rinsing thelens by spraying the lens with a rinsing solution; and, optionally,drying the lens. Similar to the dip-coating process, the spray-coatingprocess may then be repeated with a second polyionic material, with thesecond polyionic material having charges opposite of the charges of thefirst polyionic material.

The contacting of lens with solution, either polyionic material orrinsing solution, may occur by a variety of methods. For example, thelens may be dipped into both solutions. One preferred alternative is toapply the solutions in an spray or mist form. Of course, variouscombinations may be envisioned, e.g., dipping the lens in the polyionicmaterial followed by spraying the rinsing solution.

The spray coating application may be accomplished via a number ofmethods known in the art. For example, a conventional spray coatingarrangement may be used, i.e., the liquid material is sprayed byapplication of fluid, which may or may not be at elevated pressure,through a reduced diameter nozzle which is directed towards thedeposition target.

Another spray coating technique involves the use of ultrasonic energy,e.g., wherein the liquid is atomized by the ultrasonic vibrations of aspray forming tip and thereby changed to a spray, as in U.S. Pat. No.5,582,348, which is incorporated herein by reference.

Yet another method is electrostatic spray coating in which a charge isconveyed to the fluid or droplets to increase the efficiency of coating,one example of which is described in U.S. Pat. No. 4,993,645, which ishereby incorporated by reference.

A further method of atomizing liquid for spray coating involves purelymechanical energy, e.g. via contacting the liquid with a high speedreciprocating member or a high speed rotating disk, as in U.S. Pat. No.4,923,123, which is incorporated herein by reference.

Still another method of producing microdroplets for spray coatingsinvolves the use of piezoelectric elements to atomize the liquid.Examples of spray coating techniques and devices employing piezoelectricelements are given in U.S. Pat. Nos. 5,530,465, 5,630,793 and 5,624,608,all of which are incorporated by reference.

Some of the previously-described techniques may be used with air assistor elevated solution pressure. In addition, a combination of two or moretechniques may prove more useful with some materials and conditions.

A preferred method of spray application involves dispensing thepolyanion or polycation solution using a metering pump to an ultrasonicdispensing head. The polyion layer is sprayed so as to allow the surfacedroplets to coalesce across the material surface. The “layer” may thenbe allowed to interact for a period of time or immediately rinsed withwater or saline rinse (or other solution devoid of polyanion orpolycation).

A person having ordinary skill in the art will be able to select one ormore spray coating methods without undue experimentation given theextensive teachings provided herein. Accordingly, the invention is notlimited to the particular spray coating technique which is employed.

B. Coating Materials

1. Polyionic Materials

A preferred first polyionic material is a polycationic material, i.e., apolymer having a plurality of positively charged groups along thepolymer chain. For example, polycationic materials may be selected fromthe group consisting of:

-   -   (a) poly(allylamine hydrochloride) (PAH)

-   -   (b) poly(ethyleneimine) (PEI)

-   -   (c) poly(vinylbenzyltriamethylamine) (PVBT)

-   -   (d) polyaniline (PAN or PANI) (p-type doped) [or sulphonated        polyaniline]

-   -   (e) polypyrrole (PPY) (p-type doped)

-   -   (f) poly(pyridinium acetylene)

A preferred second polyionic material is a polyanionic material, i.e., apolymer having a plurality of negatively charged groups along thepolymer chain. For example, polyanionic materials may be selected fromthe group consisting of

-   -   (a) polymethacrylic acid (PMA)

-   -   (b) polyacrylic acid (PAA)

-   -   (c) poly(thiophene-3-acetic acid) (PTAA)

-   -   (d) poly(4-styrenesulfonic acid) or sodium poly(styrene        sulfonate) (PSS or SPS)

The foregoing lists are intended to be exemplary, but clearly are notexhaustive. A person having ordinary skill in the art, given thedisclosure and teaching herein, would be able to select a number ofother useful polyionic materials.

The molecular weight of the polyionic materials may be varied in orderto alter coating characteristics, such as coating thickness. As themolecular weight is increased, the coating thickness generallyincreases. However, as molecular weight increases, the difficulty ofhandling increases. In order to achieve a balance of coating thicknessand material handling, the polyionic materials preferably have a numberaverage molecular weight of about 10,000 to about 150,000. Morepreferably, the molecular weight M_(n) is about 25,000 to about 100,000,and even more preferably 75,000 to 100,000.

2. Polyallyl Amines

A particularly preferred set of polyionic materials useful in accordancewith the present invention are derivatives of a polyallyl amine having aweight average molecular weight of at least 2000 that, based on thenumber of amino groups of the polyallyl amine, comprises fromapproximately 1 to 99% of units of formula

wherein R is C₂-C₆-alkyl which is substituted by two or more same ordifferent substituents selected from the group consisting of hydroxy,C₂-C₅-alkanoyloxy and C₂-C₅-alkylamino-carbonyloxy. R is preferablylinear C₃-C₆-alkyl, more preferably linear C₄-C₅-alkyl, and mostpreferably n-pentyl which is in each case substituted as defined above.

Suitable substituents of the alkyl radical R are —OH, a radical—O—C(O)—R₁ and/or a radical —O—C(O)—NH—R₁′ wherein R₁ and R₁′ are eachindependently of the other C₁-C₄-alkyl, preferably methyl, ethyl or n-or iso-propyl, and more preferably methyl or ethyl. Preferredsubstituents of the alkyl radical R are hydroxy, acetyloxy,propionyloxy, n- or iso-butanoyloxy, methylaminocarbonyloxy orethylaminocarbonyloxy, especially hydroxy, acetyloxy or propionyloxy andin particular hydroxy.

A preferred embodiment of the invention relates to units of formula (1),wherein R is linear C_(p)-alkyl comprising p same or differentabove-mentioned substituents, and p is 2, 3, 4, 5 or 6, preferably 4 or5 and in particular 5. R is even more preferred C_(p)-alkyl comprising phydroxy groups which may be partly or completely acetylated, and p is 4or 5, in particular 5. Particular preferred radicals R are1,2,3,4,5-pentahydroxy-n-pentyl or 1,2,3,4,5-pentahydroxy-n-pentylwherein the hydroxy groups are partly or completely acetylated.

The polymers of the invention are derivatives of a polyallyl amine that,based on the number of amino groups of the polyallyl amine, comprisefrom about 1 to 99%, preferably from 10 to 80%, more preferably, from 15to 75%, even more preferably 20 to 70% and in particular 40 to 60%, ofunits of formula (1). The polymers of the invention are advantageouslywater-soluble.

A preferred group of polyallyl amine polymers comprise at least 1%, morepreferably at least 5% and most preferably at least 10%, of units offormula (1a), based on the number of amino groups of the polyallylamine.

A preferred group of polyallyl amine polymers have a weight averagemolecular weight of, for example, from 2000 to 1000000, preferably from3000 to 500000, more preferably from 5000 to 150000 and in particularfrom 7500 to 100000.

The polyallyl amine polymers may be prepared in a manner known per se.For example, a polyallyl amine having a weight average molecular weightof at least 2000 that comprises units of the above formula (1a), may bereacted with a lactone of formula

wherein (alk) is linear or branched C₂-C₆-alkylene, the sum of(t1+t2+t3) is at least 1, and R₁ and R₁′ are as defined above, to yielda polyallyl amine polymer comprising units of formula (1) and (1a).

The reaction between the polyallyl amine and the lactone may beperformed in a manner known per se; for example, the polyallyl amine isreacted with the lactone in an aqueous medium at a temperature fromabout 20 to 100° C. and preferably 30 to 60° C. The ratio of units offormula (1) and (1a) in the final polymer is determined by thestoichiometry of the reactands. The lactones of formula (6) are known ormay be prepared according to known methods. Compounds of formula (6)wherein t2 or t3 is 1 are for example available by reacting therespective hydroxy compound of formula (6) with a compound R₁—C(O)X orR₁′-NCO under conditions well-known in the art. Polyallyl amine startingmaterials of different molecular weights are commercially available e.g.in form of the hydrochloride. Said hydrochloride is converted previouslyinto the free amine, for example, by a treatment with a base, forexample with sodium or potassium hydroxide solution.

Polyallyl amines comprising additional modifier units may be prepared byadding to the reaction mixture of the polyallyl amine and the compoundof formula (6) simultaneously or preferably successively one or moredifferent compounds, for example, from the group of

wherein X is halogen, preferably chlorine, (alk′) is C₁-C₁₂-alkylene,R₁₂ is hydrogen or C₁-C₂-alkyl, preferably hydrogen or methyl, and R₃,R₄, R₅, R₅′, R₆ and Q₁ are as defined above. The reaction proceeds, forexample, in an aqueous solution at room temperature or at elavatedtemperature of for example 25 to 60° C. and yields polymers comprisingunits of formula (2a) [with compounds of formulae (6a), (6b) or (6c)],units of formula (2b) [with compounds of formulae (6d), (6e)], units offormula (2c) [with compounds of formula (6f)], units of formula (2d)[with compounds of formula (6g)] or units of formula (2e) [withcompounds of formulae (6h), (6i), (6j) (6k)].

Since the reaction of the amino groups of the polyallyl amine with thecompounds of formulae (6) or (6a)-(6k) proceeds in generalquantitatively, the structure of the modified polymers is determinedmainly by the stoichiometry of the reactands that are employed into thereaction.

A particularly preferred polyionic material is polyallylaminegluconolactone, as shown in formula 7. Particularly preferred is apolyallyl amine wherein about 20 to 80% of the amino groups have beenreacted with delta-glucolactone to yield R groups of the formula shownin formula 7.

In a preferred embodiment, the surface treatment methods of the presentinvention involve the steps of (a) applying a coating of a cationic PEI,(b) applying a coating of an anionic PAA, and (c) applying a cationiclayer of polyallyl amine gluconolactone. In another preferredembodiment, steps (b) and (c) are repeated a plurality of times,preferably about 2 to 7 times, more preferably about 3 to 5 times.

C. Coating Functions, Characteristics and Theory

Separate from the charged nature of the polyionic material, a widevariety of polyionic materials may be useful in producing a wide varietyof product properties. For example, for extended wear contact lenses,particularly preferred polyionic materials are hydrophilic, or thosewhich generate a hydrophilic surface coating, in order to inhibitadhesion of the lens to the surface of the wearer's eyes. Another classof polyionic materials useful for biomedical applications generally, andophthalmic lenses in particular, are those which exhibit antimicrobialproperties. Antimicrobial polyionic materials include polyquaternaryammonium compounds, such as those described in U.S. Pat. No. 3,931,319,issued to Green, et al. (e.g., POLYQUAD®). Yet another class ofpolyionic materials useful for ophthalmic lenses are those havingradiation-absorbing properties, such as visibility tinting agents, iriscolor modifying dyes, and ultraviolet (UV) light tinting dyes. Still afurther example of useful coating materials are those polyionicmaterials which inhibit or induce cell growth. Cell growth inhibitorswould be useful in devices which are exposed to human tissue for anextended time with an ultimate intention to remove (e.g., catheters),while cell growth inducing polyionic materials would be useful inpermanent implant devices (e.g., artificial corneas). Yet a furtherpotential functional class of coating materials are those which absorbradiation, e.g., ultraviolet (UV) light blockers. There are a number ofother biomedical applications of the present coatings processes, and aperson having ordinary skill in the art could conceive of these withoutdeparting from the spirit and scope of the present invention.

The processes of the present invention allow for production of anophthalmic lens having a core material and a surface coating. Thesurface coating includes at least one layer of polyelectrolytes, and ina preferred embodiment, at least one bilayer. A bilayer includes a firstpolyionic material which is bonded to the core material and a secondpolyionic material, having charges opposite of the charges of the firstpolyionic material, which is bonded to the first polyionic material.

It has been unexpectedly found that polymeric materials which have notheoretical ionic charges on their surfaces, or no substantial amount ofactual charges, may be coated in accordance with the present process.Teachings of in the electronics industry of methods of dip-coatingelectronics components into solutions of polyionic materials indicatehighly charged surfaces (e.g., glass) are required for proper adhesionof charged polymeric materials. However, it has been found that multiplelayers of wear-resistant coatings may be deposited onto contact lenssurfaces which are not highly charged, and even on surfaces which haveno substantial theoretical charge density. It was quite unexpected tofind that no preliminary treatments (e.g., plasma) were required togenerate charges on the lens surface in order to ensure the chargedpolymers adhered to the lens surface.

Thus, one embodiment of the present invention is directed to coatingcore lens materials which have a surface charge density in the range ofcontact lenses (especially siloxane-containing lenses) in the absence ofpreceding surface treatments. Thus, one embodiment of the presentinvention is directed to coating core lens materials which have asurface charge density which is essentially unaltered, i.e., less than asurface charge density of a material which has been previously treatedto increase charge density.

While the claimed invention is not limited to the theory developed tosupport this unexpected result, a proposed theory is presented herein inorder to enable the reader to better understand the invention. Theelectronic component treatment art teaches that extensive surfacepreparation processes are required to produce a highly positively ornegatively charged surface which will attract the oppositely chargedgroups of a polyionic coating material. However, it has beenunexpectedly found that theses extensive pretreatment processes areunnecessary for ophthalmic lenses, and in fact, that uncharged orsubstantially uncharged surfaces may be coated by contacting theuncharged surface with a highly charged polyionic species. In view ofthis unexpected finding, it is believed that a very small number ofcharges may exist in a transitory or permanent disperse state in anymaterial, such as a core lens material, and it is this small number ofcharges which allow the highly charged polyionic material to bind to thecore lens material.

One proposed explanation is that the core lens material has a lowdensity of transitory negative charges on surface, while polycationicmaterial has a high density of permanent positive ions along the polymerbackbone. While there are very few negative charges, and the charges aretransitory in nature (i.e., a particular location is only charged for asmall fraction of time), nonetheless it is believed that substantiallyall of negative charges are associated with a positive charge onpolycationic material.

Further, it is believed that the overall number of transitory orpermanent negative charges over the lens surface does not changesubstantially with time, i.e., the negative charge density on thesurface is essentially constant, but the position or location may betransitory. Thus, while the negative charges may be transitory, i.e.,the charges appear and disappear across the surface over time, theoverall number of charges is essentially constant. In view of theunexpected experimental results, it is theorized that the if thelocation of negative charges on the surface is transitory, thetransitory nature is not a problem for polycationic binding strength(i.e., coating durability) because as one negative charge disappears,and an ionic bond is lost, another negative charges appears elsewhere,and another ionic bond is formed with the polycationic material.

Alternatively, the charges on the surface of the lens polymer may bepermanent but highly disperse. Again, although the charge density istheoretically very low, whether permanent or transitory in nature, ithas been unexpectedly found that this very low charge density is stillsufficient to allow the polyelectrolyte material to bind to the surfaceof the lens with sufficient strength for ophthalmic applications.Namely, subsequent cleaning and disinfecting of the lens, as well aswearing and handling of the lens, with the associated and unavoidablesurface abrasion, does not substantially damage the polyelectrolytecoatings of the present invention.

However, in order to compensate for the low charge density of the corelens polymer, the charge density of the polyionic coating material ispreferably relatively high.

The charge density of the polyionic material may be determined by any ofa number of means known in the art. For example, the charge density maybe determined by Streming Zeta Potential.

D. Solution Characteristics and Application

The concentration of the spray or dip solution may vary depending on theparticular polyionic materials involved, the desired coating thickness,and a number of other factors. However, it is generally preferred toformulate a relatively dilute aqueous solution of polyionic material. Apreferred polyionic material concentration is about 0.001 to about 0.25weight percent, more preferably about 0.005 to about 0.10%, and mostpreferably about 0.01 to about 0.05%.

In order to maintain the polyionic material in a highly charged state,the pH of the dilute polyionic solution should be maintained at about 2to about 5, more preferably about 2.5 to about 4.5.

The rinsing solution is preferably an aqueous solution buffered at a pHof about 2 to about 7, more preferably about 2 to about 5, and even morepreferably about 2.5 to about 4.5, in order to enhance the binding ofthe polyionic material to the core or underlying polyionic material.

Partial drying or removal of excess rinsing solution from the surfacebetween solution applications may be accomplished by a number of meansknown in the art. While the lens may be partially dried by merelyallowing the lens to remain in an air atmosphere for a certain period oftime, it is preferable to accelerate the drying by application of a mildstream of air to the surface. The flow rate may be adjusted as afunction of the strength of the material being dried and the mechanicalfixturing of the material (i.e., excessive flow rates may damage thelens or dislodge the lens from the retaining means).

It should be noted that there is no requirement to completely dry thelens. The “partial drying” step, as used herein, refers to a removal ofdroplets of solution which cling to the lens surface, rather than adesiccation of the lens. Thus, it is preferred to dry only to the extentthat any water or solution film on the surface is removed.

The thickness of the coating may be adjusted by addition of one or moresalts, such as sodium chloride, to the polyionic solution. A preferredsalt concentration is about 0.1 to about 2.0 weight percent. As the saltconcentration is increased, the polyelectrolyte takes on a more globularconformation. However, if the concentration is raised too high, thepolyelectrolyte will not deposit well, if at all, on the lens surface. Amore preferred salt concentration is about 0.7 to about 1.3 weightpercent.

Thickness of the coatings may be determined by adding a dye to thepolyionic solution, e.g. methylene blue dye. Increases in visible lightabsorption correlate with increases in coating thickness. In addition,ellipsometry measurements may be used to measure the coating thickness.For hydrophilic surface modification, measurement of the contact angleof water applied to the surface gives a relative indication of surfacehydrophilicity. As contact angle decreases, hydrophilicity increases.

II. Suitable Ophthalmic Lens Core Materials

The polymeric material forming the ophthalmic lenses used in accordancewith the present invention may be any of a wide variety of polymericmaterials. However, a preferred group of materials are those materialswhich are highly oxygen permeable, such as fluorine- orsiloxane-containing polymers. In particular, the polymeric materialsdescribed U.S. Pat. No. 5,760,100, issued to Nicolson, et al. On Jun. 2,1998 are an exemplary group, and the teachings of this patent areincorporated herein by reference. For convenience of the reader,examples of suitable materials are disclosed herein, without limitationthereto.

A. Material “A”

One embodiment of a suitable core material of the present ophthalmiclenses is a copolymer formed from the following monomeric and macromericcomponents:

-   -   (a) about 5 to about 94 dry weight percent of a macromer having        the segment of the formula        CP-PAO-DU-ALK-PDMS-ALK-DU-PAO-CP        where    -   PDMS is a divalent poly(disubstituted siloxane),    -   ALK is an alkylene or alkylenoxy group having at least 3 carbon        atoms,    -   DU is a diurethane-containing group,    -   PAO is a divalent polyoxyalkylene, and    -   CP is selected from acrylates and methacrylates,        wherein said macromer has a number-average molecular weight of        2000 to 10,000;    -   (b) about 5 to about 60 weight percent        methacryloxypropyltris(trimethylsiloxy)silane;    -   (c) about 1 to about 30 weight percent of an acrylate or        methacrylate monomer; and    -   (d) 0 to 5 weight percent cross-linking agent,    -   with the weight percentages being based upon the dry weight of        the polymer components.

A preferred polysiloxane macromer segment is defined by the formulaCP-PAO-DU-ALK-PDMS-ALK-DU-PAO-CPwhere

-   -   PDMS is a divalent poly(disubstituted siloxane);    -   CP is an isocyanatoalkyl acrylate or methacylate, preferably        isocyanatoethyl methacrylate, where the urethane group is bonded        to the terminal carbon on the PAO group;    -   PAO is a divalent polyoxyalkylene (which may be substituted),        and is preferably a polyethylene oxide, i.e.,        (—CH₂—CH₂—O—)_(m)CH₂CH₂— where m may range from about 3 to about        44, more preferably about 4 to about 24;    -   DU is a diurethane, preferably including a cyclic structure,    -   where an oxygen of the urethane linkage (1) is bonded to the PAO        group and an oxygen of the urethane linkage (2) is bonded to the        ALK group;    -   and ALK is an alkylene or alkylenoxy group having at least 3        carbon atoms, preferably a branched alkylene group or an        alkylenoxy group having 3 to 6 carbon atoms, and most preferably        a sec-butyl (i.e., —CH₂CH₂CH(CH₃)—) group or an ethoxypropoxy        group (e.g., —O—(CH₂)₂—O—(CH₂)₃—).

B. Material “B”: Polysiloxane-comprising perfluoroalkyl ethers

The Material “B” macromer is defined by formula (I):P₁—(Y)_(m)-(L-X₁)p-Q-(X₁-L)_(p)-(Y)_(m)—P₁  (I)where each P1, independently of the others, is afree-radical-polymerizable group;

-   -   each Y, independently of the others, is —CONHCOO—, —CONHCONH—,        —OCONHCO—, —NHCONHCO—, —NHCO—, —CONH—, —NHCONH—, —COO—, —COO—,        —NHCOO— or —OCONH—;    -   m and p, independently of one another, are 0 or 1;    -   each L, independently of the others, is a divalent radical of an        organic compound having up to 20 carbon atoms;    -   each X₁, independently of the others, is —NHCO—, —CONH—,        —NHCONH—, —COO—, —COO—, —NHCOO— or —OCONH—; and    -   Q is a bivalent polymer fragment consisting of the segments:

-   (a)-(E)_(k)-Z—CF₂—(OCF₂)_(x)—(OCF₂CF₂)_(y)—OCF₂—Z-(E)_(k)-,    -   where x+y is a number in the range of 10 to 30;        -   each Z, independently of the others, is a divalent radical            having up to 12 carbon atoms or Z is a bond;        -   each E, independently of the others, is —(OCH₂CH₂)_(q)—,            where q has a value of from 0 to 2, and where the link —Z-E-            represents the sequence —Z—(OCH₂CH₂)_(q)—; and        -   k is 0 or 1;

where n is an integer from 5 to 100;

-   -   Alk is alkylene having up to 20 carbon atoms;    -   80-100% of the radicals R₁, R₂, R₃ and R₄, independently of one        another, are alkyl and 0-20% of the radicals R₁, R₂, R₃ and R₄,        independently of one another, are alkenyl, aryl or cyanoalkyl;        and

-   (c)X₂—R—X₂,    -   where R is a divalent organic radical having up to 20 carbon        atoms, and        -   each X₂, independently of the others, is —NHCO—, —CONH—,            —NHCONH—, —COO—, —COO—, —NHCOO— or OCONH—;            with the provisos that there must be at least one of each            segment (a), (b), and (c) in Q, that each segment (a) or (b)            has a segment (c) attached to it, and that each segment (c)            has a segment (a) or (b) attached to it.

The number of segments (b) in the polymer fragment Q is preferablygreater than or equal to the number of segments (a). The ratio betweenthe number of segments (a) and (b) in the polymer fragment Q ispreferably 3:4, 2:3, 1:2 or 1:1. The molar ratio between the number ofsegments (a) and (b) in the polymer fragment Q is more preferably 2:3,1:2 or 1:1.

The mean molecular weight of the polymer fragment Q is in the range ofabout 1000 to about 20000, preferably in the range of about 3000 toabout 15000, particularly preferably in the range of about 5000 to about12000.

The total number of segments (a) and (b) in the polymer fragment Q ispreferably in the range of 2 to about 11, particularly preferably in therange of 2 to about 9, and in particular in the range of 2 to about 7.The smallest polymer unit Q is preferably composed of one perfluorosegment (a), one siloxane segment (b) and one segment (c).

C. Material “C”

Material “C” polymers are formed by polymerizing polymerizable macromerswhich contain free hydroxyl groups. Macromers which are built up, forexample, from an amino-alkylated polysiloxane which is derivatized withat least one polyol component containing an unsaturated polymerizableside chain are disclosed. Polymers can be prepared on the one hand fromthe macromers according to the invention by homopolymerization. Themacromers mentioned furthermore can be mixed and polymerized with one ormore hydrophilic and/or hydrophobic comonomers. A special property ofthe macromers according to the invention is that they function as theelement which controls microphase separation between selectedhydrophilic and hydrophobic components in a crosslinked end product. Thehydrophilic/hydrophobic microphase separation is in the region of lessthan 300 nm. The macromers are preferably crosslinked at the phaseboundaries between, for example, an acrylate comonomer on the one handand an unsaturated polymerizable side chain of polyols bonded topolysiloxane on the other hand, by covalent bonds and additionally byreversible physical interactions, for example hydrogen bridges. Theseare formed, for example, by numerous amide or urethane groups. Thecontinuous siloxane phase which exists in the phase composite has theeffect of producing a surprisingly high permeability to oxygen.

The Material “C” polymers are formed by polymerizing a macromercomprising at least one segment of the formula (I):

in which (a) is a polysiloxane segment,

-   -   (b) is a polyol segment which contains at least 4 C atoms,        Z is a segment (c) or a group X₁,    -   (c) is defined as X₂—R—X₂, wherein    -   R is a bivalent radical of an organic compound having up to 20 C        atoms and    -   each X₂ independently of the other is a bivalent radical which        contains at least one carbonyl group,    -   X₁ is defined as X₂, and    -   (d) is a radical of the formula (II):        X₃-L-(Y)_(k)—P₁  (II)        in which P_(i) is a group which can be polymerized by free        radicals;    -   Y and X₃ independently of one another are a bivalent radical        which contains at least one carbonyl group;    -   k is 0 or 1; and    -   L is a bond or a divalent radical having up to 20 C atoms of an        organic compound.

A polysiloxane segment (a) is derived from a compound of the formula(III):

in which

-   -   n is an integer from 5 to 500;    -   99.8-25% of the radicals R₁, R₂, R₃, R₄, R₅ and R₆ independently        of one another are alkyl and 0.2-75% of the radicals R₁, R₂, R₃,        R₄, R₅ and R₆ independently of one another are partly        fluorinated alkyl, aminoalkyl, alkenyl, aryl, cyanoalkyl,        alk-NH-alk-NH₂ or alk-(OCH₂)_(m)—(OCH₂)p-OR₇,    -   R₇ is hydrogen or lower alkyl, alk is alkylene, and    -   m and p independently of one another are an integer from 0 to        10, one molecule containing at least one primary amino or        hydroxyl group.

The alkylenoxy groups —(OCH₂CH₂)_(m) and —(OCH₂)_(p) in the siloxane ofthe formula (III) are either distributed randomly in a ligandalk-(OCH₂CH₂)_(m)—(OCH₂)_(p)—OR₇ or are distributed as blocks in achain.

A polysiloxane segment (a) is linked a total of 1-50 times, preferably2-30 times, and in particular 4-10 times, via a group Z with a segment(b) or another segment (a), Z in an a-Z-a sequence always being asegment (c). The linkage site in a segment (a) with a group Z is anamino or hydroxyl group reduced by one hydrogen.

D. “Material D”

Another useful core material involves the polymerization of asiloxane-containing macromer which is formed from apoly(dialkylsiloxane) dialkoxyalkanol having the following structure:

where n is an integer from about 5 to about 500, preferably about 20 to200, more preferably about 20 to 100;

-   -   the radicals R₁, R₂, R₃, and R₄, independently of one another,        are lower alkylene, preferably C₁-C₆ alkylene, more preferably        C₁-C₃ alkylene, wherein in a preferred embodiment, the total        number of carbon atoms in R₁ and R₂ or in R₃ and R₄ is greater        than 4; and    -   R₅, R₆, R₇, and R₈ are, independently of one another, are lower        alkyl, preferably C₁-C₆ alkyl, more preferably C₁-C₃ alkyl.

The general structure of the Material D macromer follows:ACRYLATE-LINK-ALK-O-ALK-PDAS-ALK-O-ALK-LINK-ACRYLATEwhere the ACRYLATE is selected from acrylates and methacrylates; LINK isselected from urethanes and dirurethane linkages, ALK-O-ALK is asdefined above (R₁—O—R₂ or R₃₀—R₄), and PDAS is a poly(dialkylsiloxane).

For example, a Material D macromer may be prepared by reactingisophorone diisocyanate, 2-hydroxyethyl(meth)acrylate and apoly(dialkylsiloxane) dialkoxyalkanol in the presence of a catalyst.

III. Biomedical Products

In addition to the coated ophthalmic lenses described herein above, thepresent invention may be applied in alternative ways in a biomedical(e.g., ophthalmic lens) manufacturing environment. For example, one ormore polyionic materials may be added to the ophthalmically compatiblesolution in which a contact lens is stored after manufacturing.

Subsequent to molding a contact lens, the lens may be subjected toseveral post-molding treatments including, for example, additionalcuring steps, extraction, inspection and edging. Ultimately, the lenswill be placed into a container or package with a sterile,ophthalmically compatible solution for storage. In accordance with thepresent invention, a polyionic material may be added to the storagesolution, either before or after sterilization. In a preferredembodiment, a storage solution including a polyionic material is addedto a lens container along with a contact lens, the container is sealed,and the container is subjected to a sterilization process (e.g.,autoclaving).

Thus, an embodiment of the invention is an ophthalmic product thatincludes packaging retaining a contact lens and a sterile ophthalmicallycompatible solution, which includes a polyionic material, a tonicityadjusting agent (e.g., sodium chloride to produce a substantiallyisotonic solution) and water.

Another exemplary utility of the present invention is to provide a meansfor attaching materials to the surface of a biomedical device. Morespecifically, the methods of the present invention may be used to form apolyionic coating on a biomedical device, and another material may thenbe affixed to the polyionic coating via a number of means, such aschemical reaction via functional groups.

For example, a poly(ethyleneimine) [PEI] coating may be deposited ontothe surface of a contact lens via the methods described herein.Utilizing the amine functional groups, another material (e.g.,hyaluronic acid), having chemical groups reactive with amine groups, maybe chemically bonded to the PEI coating.

Thus, yet another embodiment of the invention is a method of alteringthe surface of a material by applying a polyionic coating havingfunctional groups to the surface and subsequently contacting thepolyionic coating with a second coating material having groups reactivewith the functional groups, thereby chemically reacting the groups andbonding the second coating material to the polyionic coating. Clearly, anumber of surface treatment regimes may be envisioned given theteachings of this dual treatment method, and such regimes are within thescope of the invention.

Still a further embodiment of the invention relates to the insertion ofintraocular lenses into the eye. Intraocular lenses (IOLs), as usedherein, include lenses which are designed to replace the crystallinelens in the capsule sac of the eye (e.g., used in cataract surgery) andrefractive lenses designed for vision correction and placed in theposterior or anterior chamber of the eye. The polyionic materials andmethods disclosed herein may be used to coat the insert guides,plungers, triggers and IOL assemblies to reduce friction or increaselubricity. Increased lubicity may reduce the difficulty which theophthalmologist experiences when attempting to insert the IOL into theeye.

IV. Manufacturing Processes

The present invention may also be utilized more generally in themanufacturing of biomedical articles, such as ophthalmic lenses, wounddressings, transdermal drug delivery devices, and the likepolymeric-based materials.

For example, the present invention may be used to surface treat afixture which supports an article during a manufacturing process. Thesurface treatment may be useful in increasing lubricity of the surfacesof the fixture which contact the article, thereby reducing adhesion orpromoting separation of the article from the fixture. Alternatively, thesurface treatment may increase adherence of or attraction of the fixturesurface to the article, thereby aiding in retaining the article on thefixture during a transportation or indexing step in the manufacturingprocess. A number of other functions of the surface treatment may beenvisioned, such as antimicrobial activity and antifouling.

Thus, another embodiment of the invention is a fixture for supporting anarticle which is coated with a polyionic material. The fixture surfaceshould be formed from a material having a plurality of transitory orpermanent charges on or near the surface of the material. The polyionicmaterial may be affixed to the surface by contacting therewith via anynumber of methods described hereinabove.

Another exemplary use of the present invention in a manufacturingsetting involves the coating of a mold used to define the shape of anarticle. The mold may be coated for a number of purposes, includingimportantly, quick-release from the molded article after the article isformed. The mold may be coated by any of the previously-mentionedmethods. Therefore, another embodiment of the invention is a mold formanufacturing an article, including a material having a plurality oftransitory or permanent charges on or near the surface of the materialand a surface coating, including a polyionic material which is bonded tothe core material.

Still another method of utilizing the present technology in amanufacturing setting can be termed the transfer grafting of a polyioniccoating. In this embodiment, the mold is coated with a polyionicmaterial as described above, but at least a portion of the coating istransferred from the mold when the liquid molding material (e.g.,polymerizable material) is dispensed into the mold for formation of thesolid article. Hence, another embodiment of the invention is a method offorming an article and coating the article by transfer grafting acoating material from the mold in which the article was produced. Thismethod includes the steps of applying a coating of a polyionic materialto a mold by contacting at least a portion of the mold with a solutionof polyionic material, dispensing a liquid molding material into themold, thereby contacting said liquid molding material with said coating,allowing the mold coating to contact the liquid molding material for atime sufficient for at least a portion of the coating to transfer fromthe mold to the molding material, and causing the liquid mold materialto harden (e.g., by polymerization via application of UV light).

The previous disclosure will enable one having ordinary skill in the artto practice the invention. In order to better enable the reader tounderstand specific embodiments and the advantages thereof, reference tothe following examples is suggested.

EXAMPLE 1

Siloxane-containing contact lenses were prepared in substantialaccordance with the teachings regarding “Material B” of PCT PublicationNo. WO 96/31792 by inventors Nicolson, et al. at pages 30-41, with aprepolymerization mixture having weight percentages of 50% macromer, 20%TRIS, 29.5% DMA, and 0.5% Darocur 1173. The contact lenses wereextracted and autoclaved. The average (n=20) contact angle (Sessleprop), as measured by a VCA 2500 XE contact angle measurement device(AST, Inc., Boston, Mass.) was about 111. Results are reported in TableA.

EXAMPLE 2

A lens prepared in accordance with Example 1 was surface treated with alayer-by-layer (LBL) process to increase the hydrophilicity of the lensas follows.

A dilute (10⁻² molar) aqueous stock solution of poly(allylaminehydrochloride) (50-60,000 MW_(n) from Aldrich Chemicals) [PAH] wasprepared by adding 1.3 grams of PAH to 1400 ml of deionized water. ThepH was adjusted to about 2.5 by dropwise addition of hydrochloric acid.

A dilute (10⁻² molar) aqueous stock solution of poly(acrylic acid)(50-60,000 MW_(n) from PolyScience) [PAA] was prepared by adding 4.03grams of PAA to 1400 ml of deionized water. The pH was adjusted to about4.5 by dropwise addition of hydrochloric acid.

The solution concentrations were chosen in an attempt to maintain theconcentration of positively charged units the same as the concentrationof negatively charged units.

The contact lens was immersed into the PAH application solution for aperiod of about 15 minutes. After removal from the PAH solution, thelens was immersed in three baths of deionized water adjusted to a pH of2.5 (the same pH as the PAH application solution) for two minuteperiods. Rinsing solution adhering to the lens was dislodged byapplication of a mild air stream (referred to as “drying” herein).

Next the lens was immersed into the PAA solution for a period of about15 minutes, rinsed and dried as described above.

The coating and rinsing steps were repeated an additional four times,but the drying steps were dispensed with during these coating steps.

The average (n=4) contact angle was 78. Results are reported in Tables Aand B.

EXAMPLE 3

Coated lenses as treated in Example 2 were treated by dropwise additionof 2 ml of CaCl₂ solution (9 volume percent), a strongly ionic solution,in order to determine coating durability. The lenses were dried withmild air.

The average (n=6) contact angle was 72. Results are reported in Table B.

EXAMPLE 4

A lens prepared in accordance with Example 1 is surface treated with alayer-by-layer (LBL) process to increase the hydrophilicity inaccordance with the procedures outlined in Example 2, with the followingexception: the application and rinsing solution pH for the PAA solutionwas 2.5, as opposed to 4.5 in Example 2.

The average (n=4) contact angle was 65. Results are reported in Tables Aand B.

EXAMPLE 5

Coated lenses as treated in Example 4 were treated by dropwise additionof 2 ml of CaCl₂ solution. The lenses were dried with mild air.

The average (n=4) contact angle was 76. Results are reported in Table B.

EXAMPLE 6

A lens prepared in accordance with Example 1 is surface treated with alayer-by-layer (LBL) process to increase the hydrophilicity.

A dilute (10⁻² molar) aqueous stock solution of poly(ethyleneimine)(50-60,000 MW_(n) from PolyScience) [PEI] was prepared by adding 2.00grams of PAH to 1400 ml of deionized water. The pH was adjusted to about2.5 by dropwise addition of hydrochloric acid.

A dilute PAA solution was prepared as in Example 2. The pH was adjustedto about 2.5 by dropwise addition of hydrochloric acid.

The contact lens was immersed into the PEI application solution, rinsedand dried as described in Example 2, followed by a similar treatmentwith the PAA solution.

The coating and rinsing steps were repeated an additional four times,but the drying steps were dispensed with during these coating steps.

The average (n=6) contact angle was 57. Results are reported in Tables Aand B.

EXAMPLE 7

Coated lenses as treated in Example 6 were treated by dropwise additionof 2 ml of CaCl₂ solution. The lenses were dried with mild air.

The average (n=4) contact angle was 77. Results are reported in Table B.

EXAMPLE 8

A lens prepared in accordance with Example 1 is surface treated with alayer-by-layer (LBL) process to increase the hydrophilicity inaccordance with the procedures outlined in Example 6, with the followingexception: the application and rinsing solution pH for the PAA solutionwas 4.5, as opposed to 2.5 in Example 6.

The average (n=4) contact angle was 72. Results are reported in Tables Aand B.

EXAMPLE 9

Coated lenses as treated in Example 8 were treated by dropwise additionof 2 ml of CaCl₂ solution. The lenses were dried with mild air.

The average (n=4) contact angle was 112. Results are reported in TableB.

TABLE A Rinse Primary No. of sets Secondary Primary Application SolutionApplication Secondary of Applications Avg. Example Application SolutionpH pH Drying Application Secondary Drying Contact (run) (+) (−) (+) (−)(+) (−) (+) (−) (+) (−) Applications (+) (−) Salt Angle 1 none None 1112 PAH PAA 2.5 4.5 2.5 4.5 yes yes PAH PAA 4 no no no 78 3 PAH PAA 2.52.5 2.5 2.5 yes yes PAH PAA 4 no no no 65 4 PEI PAA 2.5 2.5 2.5 2.5 yesyes PAH PAA 4 no no no 57 5 PEI PAA 2.5 4.5 2.5 4.5 yes yes PAH PAA 4 nono no 72

TABLE B Coating Coating with CaCl₂ Treatment Contact Contact ExampleAngle Example Angle 2 78 3 72 3 65 5 76 4 57 7 77 5 72 9 112

Discussion Of Results EXAMPLES 1-9

A comparison of contact angles of treated lenses in Examples 2, 4, 6 and8 with the contact angle of untreated lenses in Example 1 illustratesthat a surface modification has occurred or a coating has been deposited(See Table A). In addition, all of the treated lenses had significantlyreduced contact angles, demonstrating that the hydrophilicity of thesurface had been significantly increased.

Further, a comparison of contact angles of coated lenses in Examples 2,4, 6 and 8 with the similarly treated lenses in Examples 3, 5, 7 and 9which have been exposed to a strong ionic solution shows, with theexception of Examples 8 and 9, that the contact angles have not changedsubstantially. Thus, the surface modification or coating is unexpectedlyquite durable in the presence of a highly charged solution which wouldbe expected to dislodge charge attractions between the polyionic coatingmaterials and the contact lens surface.

EXAMPLE 10

A lens prepared in accordance with Example 1 was surface treated with anLBL process to functionalize the surface of the lens as follows.Subsequently, active species were attached to the lens via thefunctional groups provided by the LBL coating.

The lens was treated substantially in accordance with the methodsdescribed in the prior examples. The coating solutions included a firstimmersion in PEI at a pH of 3.5, a second immersion in PAA at a pH of2.5 and a final immersion in PEI, again at a pH of 3.5.

Subsequent to LBL coating, the lenses were immersed in a solution ofhyaluronic acid. It is believed that the hyaluronic acid reacted withthe free amine groups on the PEI coating, thereby bonding the hyaluronicacid to the surface of the contact lens.

EXAMPLE 11

A lens prepared in accordance with Example 1 was surface treated with anLBL process to functionalize the surface of the lens as follows.Subsequently, active species were attached to the lens via thefunctional groups provided by the LBL coating.

The lens was treated substantially in accordance with the methodsdescribed in the prior examples. The coating solutions included a firstimmersion in PEI (pH 3.5), a second immersion in PAA (pH 2.5), a thirdimmersion in PEI, a fourth immersion in PAA and a final immersion inPEI. A 2.5 bilayer structure was thus formed.

Subsequent to LBL coating, the lenses were immersed in a solution ofhyaluronic acid. It is believed that the hyaluronic acid reacted withthe free amine groups on the final PEI layer, thereby bonding thehyaluronic acid to the surface of the contact lens.

The invention has been described in detail, with reference to certainpreferred embodiments, in order to enable the reader to practice theinvention without undue experimentation. However, a person havingordinary skill in the art will readily recognize that many of thecomponents and parameters may be varied or modified to a certain extentwithout departing from the scope and spirit of the invention.Furthermore, titles, headings, definitions or the like are provided toenhance the reader's comprehension of this document, and should not beread as limiting the scope of the present invention. Accordingly, theintellectual property rights to this invention are defined only by thefollowing claims and reasonable extensions and equivalents thereof.

1. A process for making siloxane-containing contact lenses, comprisingthe steps of: a) contacting a siloxane-containing contact lens with afirst polyionic material, thereby bonding said polyionic material to thesiloxane-containing contact lens to form a coating on the surface of thesiloxane-containing contact lens, wherein the siloxane-containingcontact lens comprises a core material having no theoretical ioniccharge and is a copolymerization product of a composition including asilicone-containing monomer or macromer and a hydrophilic comonomer andwhich is not previously treated to increase its surface charge density,b) placing the siloxane-containing contact lens with the coating thereonin a container containing a packaging solution; wherein the packagingsolution comprises a tonicity adjusting agent, water and a secondpolyionic material having charges opposite of the charges of said firstpolyionic material, thereby forming a siloxane-containing contact lenshaving a polyelectrolyte bilayer; and c) sterilizing thesiloxane-containing contact lens with the polyelectrolyte bilayerthereon in the package.
 2. A process of claim 1, comprising the stepsof: a) contacting a siloxane-containing contact lens with a firstpolyionic material, thereby bonding said polyionic material to thesiloxane-containing contact lens to form a coating on the surface of thesiloxane-containing contact lens, wherein the siloxane-containingcontact lens comprises a core material having no theoretical ioniccharge and is a copolymerization product of a composition including asilicone-containing monomer or macromer and a hydrophilic comonomer andwhich is not previously treated to increase its surface charge density,b) rinsing the siloxane-containing contact lens with the coating thereonby contacting said lens with a rinsing solution, c) placing the rinsedsiloxane-containing contact lens in a container containing a packagingsolution; wherein the packaging solution comprises a tonicity adjustingagent, water and a second polyionic material having charges opposite ofthe charges of said first polyionic material, thereby forming asiloxane-containing contact lens having a polyelectrolyte bilayer; andd) sterilizing the siloxane-containing contact lens with thepolyelectrolyte bilayer thereon in the package.
 3. The process of claim1, wherein the first polyionic material is a polyanionic material. 4.The process of claim 3, wherein the polyanionic material is selectedfrom the group consisting of polymethacrylic acid, polyacrylic acid,poly (thiophene-3-acetic acid), poly (4-styrenesulfonic acid), andmixtures thereof.
 5. The process of claim 4, wherein the polyanionicmaterial is a polyacrylic acid.
 6. The process of claim 1, wherein thesecond polyionic material is a polycationic material.
 7. The process ofclaim 6, wherein the polycationic material is selected from the groupconsisting of poly (allylamine hydrochloride), polyallylaminegluconolactone, modified polyallyl amine, poly (pyridinium acetylene),and mixtures thereof, wherein the modified polyallyl amine comprisesfrom approximately 1 to 99% of units of formula

wherein R is C₂-C₆ alkyl which is substituted by two or more same ordifferent substituents selected from the group consisting of hydroxyl,C₂-C₅ alkanoyloxy and C₂-C₅ aalkylamino-carbonyloxy.
 8. The process ofclaim 7, wherein the polycationic material is a polyallylaminegluconolactone.
 9. The process of claim 1, wherein the first polyionicmaterial is a polyacrylic acid and the second polyionic material is apolyallylamine gluconolactone.